The structure of proposed binoculars, the optical diagram, optical components and their position and orientation are unchanged.
The purpose of this invention is to replace existing magnifying eyeglasses by more convenient and cosmetically attractive devices. The magnifying eyeglass improve vision for the many millions of low vision persons, including those suffering from macular degeneration.
Existing binoculars intended as low vision aids are not perfect. The Galilean type binoculars have a narrow (about 5 degrees) field of view and aberrations at the edge of the field. Existing Keplerian low vision binoculars have good optical performance but they are bulky and heavy, projecting as much as three to four inches from the eye. Some devices provide the conversion of far distance binoculars into magnifying reading glasses by putting so called reading caps on the objective lenses which enables reading but with rather small depth of sharpness.
This invention overcomes the aforementioned problems with a new type of Keplerian binoculars, each half of which is 18 mm thick (in the direction of view) and just covers the eye of the user. The whole binoculars"" appearance is similar to the appearance of sunglasses. The design is lightweight, comfortable to wear on the nose and ears. The binoculars have a front aperture of 24 mm and enable both near and far vision with high resolution.
A Special feature of the device is its convertibility. Just touching the knob no each temple side converts the far distance binoculars into magnifying reading eyeglasses. For instance, a user, during a lecture, will be able to see the blackboard and after, a quick click, be able to read his/her notebook.
The invented binoculars have two telescopes hidden in two flat containers 18 mm thick and 60 mm in diameter, covering each eye. The containers are attached to a spectacle frame. This makes the appearance of binoculars similar to that of sunglasses, as shown in FIG. 1. The binoculars are light, and the weight is distributed close to the forehead, enabling a standard eyeglass frame to be used.
Placing telescopes in small flat containers is possible because of the special optical diagram of the telescopes. The axis of the objective lens (2) and the axis of the eyepiece field lens (7) are vertical, perpendicular to the vision axis, as shown in FIG. 2. The needed long optical path from the objective lens to the eyepiece is formed by four flat mirrors positioned at 22.5 degree angle to the beam.
Conversion from far distance binoculars to magnifying reading eyeglasses without changing the magnification is accomplished by using an additional plus lens (10) inserted approximately in the middle of the optical path. This method provides at least twice larger depth of sharpness than reading cups put on the objective lens. The additional converting lens (10) is driven by a spring mechanism with a knob on the temple side of the telescope.
Despite the small dimensions, the binoculars are really powerful. The front aperture is 24 mm, magnification is 6x, the field of vision is 9 degrees, the angular resolution is 20 angular seconds. The optical system is completely corrected chromatically: the objective less and the eyepiece field lens are achromatic.
Focusing for the far vision range, from 2 yards to infinity, and also for the reading distance range is performed by rotating the focusing wheel on the temple side of each telescope.
The binoculars can be redesigned for varying degrees of magnification with corresponding changes in the field of vision.